c# - 使用可变变量调用对象的属性，如 PHP

Question

在 PHP 中，我可以使用可变变量来动态访问类属性，如下所示:

class foo 
{
    public $bar = 'test';
}

$a = 'bar'; 
$obj = new foo;

echo $obj->$a; // output 'test'

我怎样才能在 C# 中做这样的事情？

Answer 1

假设:

public class Foo
{
    public String bar { get; set; }
}

// instance that you want the value from
var instance = new Foo { bar = "baz" };

// name of property you care about
String propName = "bar";

您可以使用:

// Use Reflection (ProperyInfo) to reference the property
PropertyInfo pi = instance.GetType()
    .GetProperty(propName);

// then use GetValue to access it (and cast as necessary)
String valueOfBar = (String)pi.GetValue(instance);

最终结果:

Console.WriteLine(valueOfBar); // "baz"

---

让事情变得更简单:

public static class PropertyExtensions
{
    public static Object ValueOfProperty(this Object instance, String propertyName)
    {
        PropertyInfo propertyInfo = instance.GetType().GetProperty(propertyName);
        if (propertyInfo != null)
        {
            return propertyInfo.GetValue(instance);
        }
        return null;
    }

    public static Object ValueOfProperty<T>(this Object instance, String propertyName)
    {
        return (T)instance.ValueOfProperty(propertyName);
    }
}

并给出与上述相同的假设:

// cast it yourself:
Console.WriteLine((String)instance.ValueOfProperty(propName)); // "baz"

// use generic argument to cast it for you:
Console.WriteLine(instance.ValueOfProperty<String>(propName)); // "baz"